1. Technical Field of the Invention
The present invention relates to an image scanning apparatus, an image forming apparatus and an image scanning method, and particularly to an image scanning apparatus, an image forming apparatus and an image scanning method for automatically and continuously scanning plural sheets of originals.
2. Related Art
As an image scanning apparatus such as a scanner or an image forming apparatus such as a copy machine, there is an apparatus having the function of rotating the orientation of scanned image data in accordance with a user's designation. With this function, for example, even for an original that is too large in size and therefore cannot be physically rotated on the original table, such as an A3-size original, the orientation of image data after being scanned can be rotated into a desired direction. Also, in the case of double-side scanning of plural sheets of originals on which double-side printing has been done for left-right binding or top-bottom binding, by using an automatic document feeder (ADF), the image data of all the pages can be aligned in the same orientation by rotating the orientation of scanned image data every other sheet.
However, in the case of inputting originals at a time by an ADF or the like, the originals are not necessarily inputted constantly in a regular orientation. In such cases, even if image data is rotated only in the orientation designated by the user, a multi-page file is eventually generated in which misalignment remains. Also, in the case where plural sheets of originals on which double-side printing has been done for left-right binding or top-bottom binding include an original inverted in the top-bottom direction or left-right direction, the orientation of all the pages cannot be aligned simply by rotation processing in the regular orientation. Of course, it is possible that the user designated the rotating direction for each page, but the operation burden on the user is large.
Meanwhile, JP-B-3343367 or the like discloses a technique of automatically determining the direction of a scanned original and enabling automatic alignment of the direction in the case where originals of different directions exist. Generally, originals may be vertically long originals and laterally long originals. Moreover, in the case of Japan, for both vertically long originals and horizontally long originals, there can be originals containing vertically written characters and originals containing laterally written characters. The techniques disclosed in JP-B-3343367 include a technique of detecting a blank area at the edge of an original, punch holes, staple holes and so on and determining the type and direction of a vertically long original or a horizontally long original, a technique of recognizing characters of a scanned character image, then collating it with a dictionary, and thereby determining the type and direction of vertically written characters or horizontally written characters, and so on.
However, in such automatic determination techniques, determination errors can necessarily occur. Generally, in many automatic determination techniques, basic determination processing based on regularity that can usually be expected and exception determination processing to deal with an exception that does not meet the regularity are often combined. However, it is practically impossible to cover all exceptions. For particular originals that cannot be covered by exception determination processing, determination errors necessarily tend to occur. Also, determination errors tend to occur for stained originals and blurred originals.